"This article presents an experiment in time series analysis, specifically
the Rayleigh Test, applied to the ancient Egyptian calendars of lucky
and unlucky days recorded in papyri P. Cairo 86637, P. BM 10474
and P. Sallier IV. The Rayleigh Test is used to determine whether
the lucky and unlucky days are distributed randomly within the year,
or whether they exhibit periodicity. The results of the analysis show
beyond doubt that some of the lucky days were distributed according
to a lunar calendar. The cycles of the moon thus played an important
role in the religious thinking of the Egyptians. Other periods found
using the Rayleigh Test are connected to the civil calendar, the
mythological symbolism of the twelfth hour of the day and possibly
the period of variation of the star Algol."